What are SDH subtitles, and when should you remove the extra text?

What SDH means

SDH stands for subtitles for the deaf and hard of hearing. Besides the dialogue, they describe sounds that matter to the story, such as [phone ringing] or (whispers), name speakers who are off screen, and mark music and lyrics, often with ♪. They are written for people who cannot hear the audio, and they also help anyone watching with the sound off.

SDH, closed captions and regular subtitles

Closed captions began on television and were shown with their own technology, often as white text on a black box. SDH carry the same kind of information but are delivered and displayed like ordinary subtitles, so they work with players and discs that do not support captions. Regular subtitles usually assume the viewer can hear and translate or transcribe only the dialogue.

The labels are not used consistently. Many downloadable subtitle files called CC or English are SDH in practice, and the only way to know is to open them and look for bracketed sound descriptions.

When a clean version helps

People who can hear the audio sometimes find the extra text distracting, especially on a small screen. Translators often start from a clean dialogue file, and editors may want only the spoken words for a transcript. The subtitle cleaner removes bracketed descriptions, music marks and speaker labels, and can join repeated captions.

Keep the original too

Cleaning removes information that some viewers need. If you share subtitles with others, offer both versions rather than replacing the SDH file, and name them clearly, for example film.en.sdh.srt and film.en.srt.